In general, in fabricating a semiconductor device, various processes such as film formation, pattern etching, and the like, are repeatedly performed on a semiconductor wafer to fabricate a desired device. As semiconductor devices are required to be highly integrated and fine, a line width or a hole diameter is increasingly reduced. According to one related art, as a material of a wiring or a material to be buried in a recess such as a trench, a hole, or the like, copper, which has very small electric resistance and is low-priced, tends to be used since it is necessary to reduce electric resistance due to the reduction in various dimensions. Also, when copper is used as a wiring material or buried material, a tantalum (Ta), tantalum nitride film (TaN), or the like is generally used as a barrier layer in consideration of diffusion barrier properties, or the like of copper thereunder.
In order to bury copper in the recess, in a plasma sputtering apparatus, a thin seed film formed of a copper film is first formed on the entire surface of the wafer including all the faces of the wall within the recess, and the entire surface of the wafer is then plated with copper. Accordingly, the interior of the recess is totally buried. Thereafter, the remaining copper thin film on the surface of the wafer is polished and removed through chemical mechanical polishing (CMP), or the like.
Recently, various techniques have been developed to further improve the reliability of the barrier layer. Among them, a self-formation barrier layer using a manganese (Mn) film or a copper-manganese (CuMn) alloy film, instead of Ta film or TaN film, has come to prominence in another related art. The Mn film or CuMn alloy film are formed through sputtering, and the Mn film or CuMn alloy film itself is used as a seed film. Thus, a Cu-plated layer may be formed directly at an upper portion of the Mn film or the CuMn alloy film, and after plating the Cu plated layer, annealing may be performed. Then, the Cu-plated layer is reacted with an SiO2 layer, the underlying insulting film, in a manner of self-alignment to form a barrier film called MnSixOy (where x and y are each a certain positive integer) or MnOx (where x is a certain positive integer), a manganese oxide, at the boundary between the SiO2 layer and the Mn film or the CuMn alloy film. Namely, the number of fabrication processes can be reduced.
However, the method of forming the Cu film or the CuMn alloy film through sputtering does not have good coverage, which may fail to sufficiently cope with the trend of fabricating a highly fine semiconductor device. Thus, recently, research for forming these films according to CVD has been conducted. Also, multiple types of manganese oxides such as MnO, Mn3O4, Mn2O3, MnO2, or the like exist depending on the degree of Mn, which will be generally referred to as MnOx in the present specification.
Here, as mentioned above, when forming the Mn film and the CuMn alloy film by using a film forming device, a thermal CVD method is generally used. In this case, however, a great amount of sediment adheres on an inner surface of a processing chamber of the film forming device, on a surface of an inner structure within the processing chamber, and on an inner wall or on a surface of an inner structure of an exhaust pipe reaching a trap of an exhaust system, a pressure regulation valve (APC), a vacuum pump, or the like. As a result, the frequency of a cleaning process is increased or a great amount of particles is generated due to delamination of the sediment. These problems are severe because a film formation rate increases when an oxygen-containing gas such as H2O, or the like is added as a reactant gas.